binary 'operator' : no operator defined which takes a left-hand operand of type 'type' (or there is no acceptable conversion)
To use the operator, you must overload it for the specified type or define a conversion to a type for which the operator is defined. If you encounter this error while porting code from Visual C++ 2.0 or earlier, see Technote: Improved Conformance to ANSI C++.
Example
class C { public: C(); }; void main() { C aC; aC + 12; // error }